“White peat” or peat moss, coconut fibers and rock wool are widely used in horticulture and in greenhouse cultivation as substrate materials. Additionally some synthetic cultivation media have been developed, however, their use is limited.
Rock wool is manufactured from stone by heating with the technology used in the manufacture of insulation boards for construction industry. Rock wool growing medium requires constant fertilization with irrigation water. Water is not retained evenly throughout the rock wool medium. Rock wool is not recyclable by composting and it cannot be used as landfill waste.
Coconut fibers obtained from coconuts are used in the manufacture of cultivation boards, typically containing finer fibers on the top and rougher fibers at the bottom of the board to provide an even water distribution in the board. The availability of coconut fibers is limited and further, cultivation of plants sensitive to saline water may be problematic as salts are released from coconut fibers during irrigation.
Peat is widely used as growing medium in horticulture and about 30 million m3 of white peat is globally used for this purpose. White peat, also known as Sphagnum peat is fossil material and a decomposition product originating from Sphagnum moss. Peat accumulates in peat lands and bogs. In most countries in the Western and Central Europe the stocks of fossil white peat are almost depleted and peat industry has increasingly removed to the Baltic States, Scandinavia and Canada.
Peat is considered as finite and non-renewable resource, or very slowly renewable resource. It is renewed in the topmost layers of peat bogs very slowly, depending on the thickness of the layer, surrounding conditions and growth. Peat industry is generally regarded as irreversibly destroying the important nature conservation functions, particularly biodiversity and climate regulation functions, especially carbon storage. Peat is considered a carbon reservoir, but after a short period of use as a growth substrate in the greenhouse production it becomes a major carbon emitter.
Peat has ideal properties as a cultivation medium with respect to fertilization and irrigation. Used peat products may be recycled as compost and landfill waste material, and if desired, they may be burned. There is a shortage of high-quality peat in Europe. Further, peat has some antimicrobial properties and thus the growth of harmful plant diseases and bacteria can be prevented or decreased using cultivation medium based on peat; peat is also widely used as desiccant for animals.
The use of non-decomposed Sphagnum moss as growing medium is well known in the field. Sphagnum moss is commonly used for the culture of orchids. It has been suggested as plant growth medium in combination with perlite, vermicompost, compost, composted pine bark and fertilizers. Germination mats comprising a substrate including a layer comprising sphagnum moss particles and plurality of seeds situated on or incorporated in said substrate are suggested in WO 9856232. Absorbent structures containing Sphagnum moss are presented in U.S. Pat. No. 5,635,029.
Water level regulation, fertilizer regulation, particularly at greenhouses and the like, operating on a larger industrial or commercial scale with the presently available Sphagnum moss products are difficult to control and operate. Further, growth mediums comprising Sphagnum moss tend to lose their structure when roots of plants penetrate the moistened mats.
Traditional wet laid methods have been suggested for the manufacture of mats etc. comprising Sphagnum moss, but the structure of these product is not retained after irrigation.
Based on the above it can be seen that there is a need for new growing medium structures comprising Sphagnum moss, suitable for example as cultivation and growing media, said growing medium structures having advantageous cultivation properties, retaining their structure and simultaneously being cost-effective, recyclable and environmentally sustainable products.
Technique relating to producing foam-laid fiber webs is known in the field of manufacture of paper and tissue products. A fiber web is formed from a dispersion of fibers in a foamed liquid. Pulp or fiber furnish is first prepared in a breaker, followed by dewatering and mixing with a foamable liquid containing a surfactant and water whereby the fibers are dispersed in the foam. The formed dispersion is deposited on to a foraminous support, which allows the liquid, which is essentially in the form of foam, to drain through while retaining most of the fibers in the form of a web. This technique is disclosed for example in EP 481746.
Based on the above it can be seen that there also exists a need to provide new methods for the manufacture of growing medium structures based on Sphagnum moss.